1. (Field of the Invention)
The present invention relates to a tool clamping apparatus for clamping firmly an attachment for mounting a tool which is mounted, for example, to a part to which the tool is mounted of NC machine tools, e.g. a tool post by a manipulator of an automatic tool changer, to the afore-mentioned tool post.
2. (Description of the Prior Art)
The attachment for mounting the tool, for example, which is mounted to the tool post of a numerically controlled turret lathe by the manipulator of the automatic tool changer is equipped with a taper extruding shaft part capable of being closely fitted into a hollow taper hole of the afore-mentioned tool post. For this reason, in order to clamp the afore-mentioned attachment for mounting the tool, the afore-mentioned taper extruding shaft part which is adapted to be fitted into the afore-mentioned taper hole is pulled into an internal area, thereby fitting closely both into each other, and, if necessary, a mutual surface contact is performed between annular end faces, which are formed around a shaft center, of the side of the afore-mentioned attachment for mounting the tool and the side of the afore-mentioned tool post.
Conventionally, this kind of tool clamping apparatus has used a pulling-in shaft which may be detachably mounted to the tip end of the afore-mentioned extruding shaft and a plurality of belleville springs which pull said pulling-in shaft into the internal area as a means of pulling the taper extruding shaft part of the afore-mentioned attachment of mounting the tool. Such a clamping apparatus utilizing the conventional belleville springs give rise to an danger of loosening the clamping force for the attachment for mounting the tool in an unexpected manner so that it is problematic in terms of the safety in the case of a heavy duty cutting in which a cutting force of a cutting tool mounted to the attachment for mounting the tool is more powerful than a spring force of the afore-mentioned belleville springs, or where it is applied to the machine tools using the cutting tool which is large in extruding amount for machining. Furthermore, there is a difficulty in applying it to the attachment for mounting the tool equipped with a tool driving shaft which penetrates the central part, because it has the afore-mentioned pulling-in shaft and group of belleville springs arranged on the center line, and, generally, its possibly applicable scope is only within the machine tools whose system drives and rotates the attachment for mounting the tool itself, i.e. the machine tools equipped with the tool post which is driven to be rotated.